Traditionally, inspection to verify whether tablets packaged by a tablet packaging machine are packaged as directed by a prescription has been performed visually by pharmacists. Apparatus for assisting such visual inspection by pharmacists are disclosed, for example, in Japanese Laid-open Patent Publication No. 63-294307 and Japanese Patent Publication No. 4-17666. These apparatus are designed to inspect tablet type and tablet count by capturing an image of packaged tablets with a camera.
However, since the image of the tablets packaged in a packaging sheet is captured in two dimensions, when more than one tablet is packed in a package the above inspection apparatus have often been unable to recognize the overlapping or contacting condition of the tablets, erroneously judging the condition as a packaging defect. Furthermore, when letters are printed with white paint in a stripe pattern on the packaging sheet, it is not possible to recognize the tablets concealed behind the stripe.
These problems will not be solved even if the images are captured from both sides of the packaging sheet. In view of this, apparatus for inspecting tablets by capturing their images as they are apart from each other just before packaging are disclosed in Japanese Laid-open Patent Publication Nos. 5-337168 and 8-168727. However, the processing speed of these apparatus is slow because the tablets must be separated from one another. Furthermore, since these apparatus inspect tablets just before packaging, not after packaging, if a tablet to be packed in a packaging sheet is erroneously put in an another packaging sheet before or after it, such wrong packaging cannot be detected, and reliability of the inspection apparatus is therefore low. For example, when the type of tablets to be taken in the morning is different from the type of tablets to be taken in the afternoon, if a tablet for the afternoon is put in the packaging sheet containing the tablets for the morning, then the package will be delivered as it is to the patient. As a result, he will take the tablet at the wrong time, defeating the purpose of medication. Furthermore, if a machine part such as a screw or spring or other foreign matter such as an insect or dust gets mixed when packaging, there is a danger that the package may be delivered as it is to the patient who then may erroneously swallow it with the tablets.